Thermostat



Nov. 12, 1929. A. E. ELLIS 1,735,268

THERMOSTAT Filed Feb. 8, 1925 Invent '0 .Hxe? E..Elli8} Patented Nov.12, 1929 UNITED STATES PATENT OFFICE,

AXEL E. ELLIS, OI BOSTON, MASSACHUSETTS, ASSIGNOR TO M. W. BARBER,HORACE D. EVER T AND GEORGE SIEGEL, BOARD OF TRUSTEES IN SAIASMANUFACTURING- courm Application filed February 8, 1923. Serial No.617,718.

- Flatirons, if left for too long a time with the current turned on, aresubject to the danger ofbecoming overheated and thereby either scorchingthe garments beingironed, or even setting the table and the house afire.The object of this invention is the construction of athermostat whichcan be instantly at tached to any well known form of electric flatironhaving spaced terminal pins.

In the drawings forming part of this specification, Fig. 1 is aperspective view of a thermostat embodying my invention and mounted uponan electric flatiron. Fig. 2 is a plan view on an enlarged scale of theoperative portions o1v the thermostat. Fig. 3 is a perspective View ofthebase unprovided with the operative parts. Fig. 4 is a plan view ofthe member by means of which the thermostat is attached to the terminalpins of a fiatiron. Fig. 5 is a section on the line 55 in Fig. 4. Fig 6is a section on the line 66 in Fig. 4. Fig. 7 is a horizontal sectionpartly on the line 77 in Fig. 6, and 77 in Fig. 5. Fig. 8 :is aperspective view of one of the two sections composing the attachingblock. Fig. 9 is a perspective view on an enlarged scale of theeccentric device for adjusting the heat controlled element of thethermostat. Figure 10 is an end view of the insulating block shown inFigs. 1 and 3.

The base 1 of the thermostat carries all the operative parts, the latterbeing supported in bearings struck up from the bottom plate of the base,as shown in Fig. 3, the open top being closed by a cover 2 telescopingthereon. The operative parts include a stem 3 having a button 4 andslidable through a notch 5 in an end of the base. This stem bears a pawl6 pivoted thereto at 7, which pawl is designed to engage a shoulder 9 onthe shank 1O slidably supported .in'bearings 11, 11, a helical spring 12pressing against the shoulder 9 and bearing 11 serving to push the shankin opposition to the urging of the button 4.

' To the end of the shank 10 is attached a.

.crosshead 13 and an insulating block 14, as

shown in Fig. 2, bearing contact fingers 15,

16, preferably consisting of a single length of spring metal bent intoan inverted V and having in-turned terminals 17. When the button 4 ispressed inwardto its limit, the terminals 17 are put into touch with thecontacts 19, 20 and thereby made to complete a circuit connectedtherewith. For retaining these terminals or circuit closing element inoperative position, a spring detent 21 is provided which engages thesmall shoulder 22 in the cross head 13, provided the temperature issufficiently low, the same being composed of two unequally expandingmetals, as brass and 00 steel, in a well known manner. The foot of thisdetent 21 is bent at right angles to the main body, and attached to thebase 1 by a screw 23 passing through the end of the base and the foot 24into a nut or block 25. A pin 26 provides additional security for thesame.

For returning the stem and button 3, 4 to their normal position, ahelical spring 27 mounted on a pin 29 and bearing against a shoulder 30on the stem, serves the purpose. The pawl 6 is provided with a tail 31so proportioned that when the stem and button have been pushed inward tothe limit and the detent 21 has engaged the shoulder 22, the tail 31comes against the end of the pin 29 and thereby forces the pawl 6 out ofits engagement with the shoulder 9. The spring 27 then throws the stemand button to their outward limit. At this limit the tail 31 meets theend wall of the base 1 and thereby swings so the pawl 6 into position toengage the shoulder 9 when the parts 10, 13 and 14 are released by thedetent 21.

To adjust the detent for different degrees of temperature, I provide acam 32 formed by suitably reducing an intermediate section of a roundrod 33 whose upper part is bent over andshaped into an indicator finger34 designed to co-operate with markings on the exterior of the cover 2,as at 35. By turning the finger 34, the detent 21, which rests againstthe cam ortion 32, has its resilient pressure against t e end of theshoulder 22 is increased or diminished as desired. So long as the detentrests against the reduced portion of the cam, the detent acts as a lockto prevent the withdrawal of the cam-member, but when it is turned tothe position illustrated in Fig.

2, the cam-member can be removed if desired.

The means for attaching this thermostat to a flatiron preferablyconsists of a two-part block of insulating material, bearing terminalpins 35, 36, the part 39 receiving the pins, and the part 40 havingrecesses 41, 42 for holding spring sockets 43, 44 into the grip of whichthe terminal pins of the flatiron are to be inserted. The spring socket44 is held in place by a screw 45 which penetrates a partition 46 of theblock-section 39, and becomes a binding post for one of the lead wir'es,as 47, running to the contact 19. An insulating plate 49 separates thespring socket44 from the terminal pin 36, which is partially cut awayfor the purpose, and is bent at right angles and threaded toform asecond binding post 50 to which the lead wire 51 is attached.

The other spring socket 43 is held in place by the engagement therewithof the threaded section of the terminal pin 35, as shown in Fig. 5. Asshown in Fig. 7, both spring sockets are laterally enlarged to enableter minal pins of different distances apart to be inserted therein,difierent diameters of pins being taken care of by the resilience of thesockets.

When the bridging switch 15, 16 has closed the circuit by being put intouch with the contacts 19, 20 as above described, and the terminals ofa source of current have been engaged with the pins 35, 36, the currentpasses from the pin 35 to the spring socket 43 and thence to one of theterminal pins of the flatiron, through the heater elements in thefiatiron and back to the other terminal pin of the fiatiron. From thelatter, the current passes to the spring socket 44, to the binding post45, through the wire 47 to the contact 19, through the bridge 15, 16 tothe contact 20, from the latter through the wire 51 to the binding post50, terminal pin 36 and back through the applied leading wire to thecurrent-source.

As shown in Fig. 1, the base 1 is suspended in contact with the heel ofthe section 52 of the fiatiron which contains the heating elements,thereby transmitting the heat to the thermostat from the hottest portionof the fiatiron.

To render it visually evident that the thermostat circuit is closed, theend of the shank is prolonged in a pin 53 which, when the cross head andshank 13, 10 are in their retracted position and the circuit is broken,protrudes through a hole in the end of the base and cover 1, 2, as shownin Fig. 2. Hence whenever the pin 53 is visible the operator can knowthe circuit is broken, and when the pin is out of sight, the circuit isclosed.

As shown in Fig. 10, the insulating block 55 is channelled on twoopposite sides, the shallower channel being for the reception of thecontacts 19, 20, and the dee er one for the nuts of the screws which holthe contacts in memes place and which serve as the binding posts for thelead Wires 47, 51. This channelling of the insulating block is by farthe most economical method of manufacturing such a block in providing itwith recesses for the contacts and binding posts and nuts, since thesame can be produced in long strips and cut oil at desired lengths.

As shown in Figs. 1 and 2, the cover 2 is formed with a leaf 54 by meansof which the united cover and base are attached to the two-part block39, 40, this leaf serving also to cover the recess in which are thebinding posts 45, 50. v

In the event that the detent 21 does not engage the shoulder 22 owing tothe fact .that the temperature of the thermostat is high enough to bendthe detent out of reach of the shoulder, then the spring 12 pressingagainst the shoulder 9 instantly forces back the shank 10 and breaks thecircuit at 19, 20.

What I claim is:

1. A thermostat comprising a slidable circuit closing device, a pushbutton having a detent adapted to be engaged with said device, a springfor returning said device to normal, and a heat controlled deviceadapted when cool to engage said circuit closing device and to retain itin its circuit closing position, said detent being adapted to releasesaid device when the push button reaches the limit of its circuitclosing position.

2. A thermostat comprising a slidable circuit closing device, a slidablestem having a push button, a slender rod slidably supported bearingcircuit closing means, a spring for returning the latter to its normalposition, a heat controlled detent for retaining said circuit closingmeans in their circuit closing position when at a predeterminedtemperature, a pawl carried by said stem and adapted to engage saidslender rod, and means for tripping said pawl when said slender rod hasbeen pushed to its limit.

3. A thermostat comprising a slidable stem, a spring for its retraction,a slender rod bearing circuit closing means, a spring for returning saidrod to its normal posltion, heat controlled means for retaining saidcircuit closing means in its closing position, and a pawl carried bysaid stem an adapted to be engaged with said rod, said pawl having atail adapted to throw the pawl into and out of said engagement at therespective ends of said rod s travel.

4. A thermostat comprising a case, a slidable stem, a spring for itsretraction, a slender rod bearing circuit closing means, a spring forreturning said rod to its normal position, and heat controlled means forretaining said circuit closing means in its closin position, said casehaving a hole in line with said rod, and the latter having a pinprojecting therefrom through said hole when in its normal position.

5. A thermostat comprising a case, a slid able stem operative fromoutside said ease,

' a spring for its retraction, a slender rod bear- 6th day of February,

ing circuit closing means, a spring for returning said rod to its normalposition, and heat controlled means for retaining said circuit closingmeans his closing position, said case having a hole through its wall,and said rod having means coactmg with said hole for visually showingwhen said rod is in its normal position. v

6. In a thermostat having a case and a thermostatic element therein,aicam for the adjustment of the latter consisting of a round pin havingan intermediate portion cut away to form a cam surface bearin againstthe said element, and a handle fixe on the outer end of said pin; thesaid case having bearin rotatively recelvin said in; whereby t e lattercan be intr uced t rough said bearings from the outside of said case,and by the en agement of its cut-away portion with said e ement is helda ainst removal.

In testimony that I c aim the foregoing invention, Ihave hereunto 7 setmy hand this AXEL E. ELLIS.

